Study On Gas Shunt Of Natural Gas Engine With Dual Intake Ports And Its Influence On Combustion

The increasing air pollution and energy crisis have forced scholars in the field of internal combustion engines to seek cleaner alternative energy sources.Natural gas is considered to be one of the ideal alternative fuels due to its abundant reserves and chemical properties with little environmental pollution.Especially as a fuel for internal combustion engines,it has great advantages.Due to the higher integration of 6K natural gas engines,both the dual intake port and the intake manifold are integrated on the cylinder head,so the intake manifold is short,and most of the gas will enter the cylinder from the intake port near the nozzle.In the process,the distribution of the mixture in the cylinder is uneven,and the mixture is poorly layered,which is not conducive to the efficient and clean combustion of the engine.At the same time,it causes the problems of poor power,economic efficiency and high emissions of natural gas engines.In order to solve the problem of uneven gas mixture distribution during the intake process of a natural gas engine with dual inlets,which affects the combustion performance of the natural gas engine,three types of bifurcated gas nozzles and seven dual-type gas nozzles are designed in this paper.The independent jet injection scheme of the valve,and through the method of three-dimensional simulation calculation,the AVL FIRE software was used to explore the propulsion characteristics of the ship’s engine at 1130 r / min,25% load,1640 r / min,and 75% load.The influence of different pipe diameters of fork-type gas nozzles and seven types of dual-valve independent jet injection schemes on engine intake and combustion characteristics.The study found:For the bifurcated pipe structure,under 25% load,the short pipe and the long pipe have the best performance when the diameter of the pipe is 6mm,and the short pipe and the long pipe have the diameter of 4mm,the combustion performance is the worst,but in general The three nozzles have less influence on the combustion performance.For a bifurcated structure,under 75% load conditions,the short-pipe diameter is 4mm,and the long-pipe diameter is 6mm.However,there is not much difference in performance between the three structures.For the double-nozzle structure,under 25% load conditions,the 1 # and 7 # injections are bent-pipe independent injection and straight-pipe independent injection,respectively.The straight-pipe independent injection combustion speed is faster.The remaining five types of two nozzle injection schemes have the best combustion performance when the ratio of the curved nozzle is slightly greater than or equal to the ratio of the straight nozzle,and the performance is worse on the contrary.Under the 75% load condition,the other five types of two nozzles are sprayed,and the performance of the independent injection of the straight pipe is better than that of the elbow pipe.When the elbow injection ratio is between 20% and 50%,the injection ratio of the two nozzles has little effect on the combustion performance of the engine.When the elbow injection ratio is between 50% and 80%,the combustion is accompanied by the increase of the elbow injection ratio,speed is decreasing.